Energy sensor

ABSTRACT

AN ENERGY SENSOR INCLUDES TWO MEMBERS WHICH ARE SHIFTABLE RELATIVE TO EACH OTHER. ONE OF THE MEMBERS IS PROVIDED WITH A SOKET WHILE THE OTHER MEMBER FITS INTO THE SOCKET. A HONEYCOMB SECTION IS POSITIONED IN THE SOCKET BETWEEN THE TWO MEMBERS AND HAS ITS COLUMNS EXTENDING PARALLEL TO THE DIRECTION OF MOVEMENT BETWEEN THE MEMBERS. THE HONEYCOMB SECTION IS PRECRUSHED TO OVERCOME ITS COLUMNAR STRENGTH. THE SOCKET IS VENTED TO   ELIMINATE BACK PRESSURE WHEN THE MEMBERS MOVE RELATIVE TO EACH OTHER SO THAT THE HONEYCOMB SECTION OFFERS SUBSTANTIALLY THE ONLY RESISTANCE TO FORCES APPLIED TO THE MEMBERS.

.e/vmcr (w. LB/lN 65 Feb.23, 1971 MLLSCHMMEL HAL Re.21,073

FNERG Y S HNSOR Original Filod July 6, 1964 INVENTORS VICTOR W.DREXELIUS O -3 .6 .9 1.2 w/ v -Z/ COMPFESS/UA/ {was 5) A TTORNEYS MORRYL. SCHIMMEL ROY H. BLEIKAMP, JR.

United States latent 27,073 ENERGY SENSOR Morry L. Schimrnel, UniversityCity, Mo., and Roy H. Bleikamp, Jr., and Victor W. Drexelius,Edwardsville, lll., assignors to McDonnell Douglas Corporation, St.Louis, Mo., a corporation of Maryland Original No. 3,263,489, dated Aug.2, 1966, Ser. No. 380,553, July 6, 1964. Application for reissue June 5,1968, Ser. No. 741,816

Int. Cl. G01n 33/22 US. CI. 7335 8 Claims Matter enclosed in heavybrackets II] appears in the original patent but forms no part of thisreissue specification; matter printed in italics indicates the additionsmade by reissue.

ABSTRACT OF THE, DISCLOSURE An energy sensor includes two members whichare shiftable relative to each other. One of the members is providedwith a socket while the other member fits into the socket. A honeycombsection is positioned in the socket between the two members and has itscolumns extending parallel to the direction of movement between themembers. The honeycomb section is precrushed to overcome its columnarstrength. The socket is vented to eliminate back pressure when themembers move relative to each other so that the honeycomb section offerssubstantially the only resistance to forces applied to the members.

This invention relates to an energy sensor and more particularly to an[explosive] energy sensor which measures [explosive] energy bydeformation of a honeycomb sensing element. 7

Various energy sensors have been used in the past; some utilize plasticdeformation of small lead or copper elements, in some instances,referred to as crusher gages, and othersutiline plastic deformation ofair backed plates or diaphragms referred to as diaphragm gages.

,Briefly, the present invention includes a honeycomb section confinedwithin a cylinder by an end cap and piston. The cylinder is convenientlymounted in the path of the explosive charge such that the force of theex plosion acts on the piston moving such longitudinally in the cylinderto deform the honeycomb structure against the end cap.

It is therefore an important object of the present invention to providean energy sensor having a deformable honeycomb structure confined in anenclosure which subjects the honeycomb structure to deformation energy.

It is another object of the invention to provide an explosive energysensor having a deformable honeycomb sensing element which is relativelyinexpensive and affords reproducible results.

It is another object of the invention to provide a honeycomb sensingelement for an explosive energy sensor which affords a deformationmeasurement that varies linearly with the energy to approximately 75percent of honeycomb length.

It is another object of the invention to provide an energy sensor whichincludes a replaceable honeycomb sensing element of relativelyinexpensive material to provide a Wide range energy sensor, depending onthe strength of honeycomb selected.

It is another object of the invention to provide an explosive energysensor having a cylindrical housing, a fixed end cap mounted to saidhousing, a piston adapted to move within the housing confining ahoneycomb sens- Re. 21,073 Reissued Feb. 23, 1971 ing element againstthe end cap, the end cap and housing having apertures to avoid backpressure in the sensor, the piston adapted to move within said housingand deform the honeycomb sensing element when subjected to explosiveenergy.

Another object of the invention is to provide an explosive energy sensorhaving an energy sensor element, a cylindrical housing, a fixed end capmounted to said housing, a piston confining said element within saidhousing extended and adapted to have a mounting channel for positioninga linear explosive charge for testing purposes.

Another object of the invention is to provide an explosive energy sensorhaving an energy sensor element, a cylindrical housing, a fixed end capmounted to said housing, a piston confining said element in said housingadapted to coact with an actuator assembly designed to confine adetonator for measuring the explosive energy of such detonator.

These and other objects and advantages of the invention will becomeapparent from the description hereinafter and the appended claims, inconjunction with the drawings, wherein:

FIG. 1 is a cross-sectional view of the energy sensor;

FIG. 2 is a cross-sectional view taken along line 22 in FIG. 1;

FIG. 3 is a partly broken away view of the energy sensor including amodified piston for testing linear charges;

FIG. 4 is a partial cross-sectional view of the energy sensor includinga piston adapted to detect energy of a detonator retained within a testhousing; and

FIG. 5 is a graph depicting the typical straight line function of thehoneycomb sensing element of the energy sensor.

Referring specifically to FIGS. 1 and 2 there is illustrated thepreferred embodiment of the energy sensor, generally designated 10. Theexplosive energy sensor consists of a cylindrical housing 1 havinginternal threads 2 adapted to receive end cap 3-. The cylinder 1 hasapertures 4 to permit pressure equalization on both sides of thecylinder 1. End cap 3 has a reduced dimension shaft 5 which extends intoa face plate 6. A hollow piston 7 fits within cylinder '1 and fits overface plate 6 of end cap 3. Confined between piston 7 and face plate 6 isthe sensor element, honeycomb section 8 of square cross section. Faceplate 6 has apertures 9 therein to prevent pressure buildup betweenpiston 7 and face plate 6. Piston 7 is confined within cylinder 1 bycover 11 which has a central aperture 12. Cylinder 1 is placed againstfixed structure 15 along the edge periphery of cover 11. Cover 11threadedly engages cylinder 1 at external threads 13-.

Referring now to FIG. 3 there is illustrated explosive energy sensorgenerally designated 20 appertaining to the invention which is similarin all respects to energy sensor 10 described with reference to FIGS. 1and 2 with the exception that piston 7 of FIG. 1 is modified as piston21 in the embodiment of FIG. 3. The piston -21 extends be yond housing 1and has a face plate 22 including threaded bores 29. A holder 23 havingapertures 24 aligned with threaded bores 29 abuts face plate 22. Bolts25 retain holder 23 securely to face 22 of piston 21. The holderincludes grooves 26 which retain the linear explosive charge 27 whichmay be for example mild detonating cord or flexible linear shapedcharge, etc. The sensor 20 is positioned against a non-yieldingstructure so that the maximum derivable amount of explosive energy isabsorbed by the sensor element 8.

Referring now to FIG. 4 there is illustrated energy sensor 30, similarin principle construction to the energy sensors 510 and 20 of FIGS. 1and 3. Sensor 30 has a casing 1 which is threaded to receive end cap 3,but not cover 11. A contact plate 21 abuts piston 7 and is an integralportion of projecting ram 32. which fits within an actuator body 39. Thesensor 30 is mounted by straps 33 affixed to a mounting surface 34 bybolts 35. The actuator body 39 has a through port 36 which threadedlyreceives the detonator 40, or other explosive energy sources, such as,but not limited to squibs, pressure cartridges and igniters, to betested. The actuator body 39 is held to mounting surface 34 by bolts 37.

Typically the explosive or blast energy sensor appertaining to theinvention, and as particularly described with reference to FIG. 1, has ahoneycomb sensor element which may be of 5052 aluminum 4 inch hexagonalcells having permeations 8' to permit air passage therethrough andhaving a wall thickness of 0.0007 of an inch, with a density of 1.6pounds per cubic foot. The honeycomb is cut one inch square and 1- /2inches long. The piston 7 maybe aluminum having an internal diameter ofabout 1.46 inches and an external diameter of about 1.65 inches. Housing1 is an aluminum cylinder about four inches long and 1.659 internaldiameter. End cap 3 is aluminum and fits approximately 2.4 inches intocylinder 1, and face 9 fits within the hollow piston 7, thus having adiameter approximately the internal diameter of piston 7. Prior tocutting honeycomb section 8 to the appropriate length it is pre-cnishedabout .06 inch. The pre-crushing of the honeycomb section 8 is necessaryin order to overcome the initial high columnar strength of the sectionand put the section in a condition so that its reaction to an appliedcrushing load or force will result in a substantially uniform absorptionof the energy of such load or force.

For the particular honeycomb sensor element in the sensor constructed asmentioned above, FIG. 5 is a graph for Curve A illustrating compressionof the honeycomb sensing element in inches as the abscissa and energy ininch-pounds per square inch as the ordinate. Similar curvesfor othersuch energy sensors may be obtained by calibrating the particularstrength honeycomb sensor element used in the particular energy sensor.T ypically{ this may be done by dropping a one-pound weight from variousheights to impact against piston 7 (as depicted in FIG. 1). Thehoneycomb compression is measured at each height. From this, thecalibration curve of energy vs. compression may be obtained similar tothat illustrated in FIG. 5.

In operation, the explosive energy sensor is exposed to explosive energyalong the piston face and this energy is dissipated by deforming thehoneycomb sensing element. No pressure build-up occurs in the honeycombsensor enclosing area because of vent holes 9 and 4 and because thehoneycomb itself is permeated to permit air passage. After the sensorelement has been exposed to an explosive energy source, the compressionis determined by measurement of length of honeycomb crushed. Themeasured compression is directly proportional to the energy ininch-pounds per square inch for a range of compression up to about 75percent of honeycomb length.

-It will be appreciated that the explosive energy sensor appertaining tothe invention has been disclosed with several embodiments, and it isapparent that other modifications and changes will become readilyapparent to those skilled in the art. Therefore, such minormodifications and changes as will be suggested are deemed to be withinthe scope of the invention which is limited solely as necessitated bythe scope of the appended claims.

What is claimed is:

1. An explosive blast energy sensor comprising a housing, a fixedplunger in said housing, a piston telescopically received in saidhousing over and movable relative to the plunger, and a honeycombsection retained in said housing by and between the plunger and pistonwith its 4. honeycombs directed axially of said plunger and piston so asto be adapted to be uniformly compressed therebetween by explosiveenergy to be measured impinging on the piston said honeycomb sectionbeing pre-crushed by an amount to initially overcome its honeycombcolumnar strength, and said housing being vented to atmosphere to freesaid piston from compressing. air.

2. An energy sensor assembly for testing linear explosives comprising acasing, an end member aifixed to the casing defining a plungerprojecting Within the casing having a face plate less than the internalcasing dimension, a piston having a hollow head and having an integralconnecting rod defining a contact end, said piston retained within thecasing with the hollow head fitted about the face plate periphery andthe. connecting rod projecting from the casing, a honeycomb sensorelement confined within the hollow head of the piston by the plunger,and means to mount a linear explosive to the contact face such that oninitiation of the explosive the piston will uniformly compress thehoneycomb sensor element against the plunger.

3. The sensor assembly of claim 2 wherein the face plate defines throughports and the casing is perforated in the area about the plunger.

4. The sensor assembly of claim 3 wherein means to mount a linearexplosive includes a holder mounted to the contact face and defining asupport groove for retaining the linear explosive under testing.

5. An explosive energy sensor assembly for testing detonators or otherexplosive energy sources comprising an energy sensor device including acasing, an end member afiixed to the casing defining a plungerprojecting within the casing having a face plate less than the internalcasing dimension, a piston having a hollow head and having an integralcontact face, said piston retained within the casing with the hollowhead fitted about the face plate periphery and the contact face exposedexternal to the casing, and a honeycomb sensor element confined withinthe hollow head of the piston by the plunger; and an actuator deviceincluding a housing defining a through bore and a counterbore, adetonator holder and activating device retained within the counterbore,an actuator rod riding in the through bore and extending from thehousing, the actuator rod defining a contact plate external of thehousing adjacent in contact face for transmitting blast energy from thedetonator under test to the piston effecting compression of thehoneycomb sensor element.

6. An energy sensor assembly comprising: a housing open at one end; aface plate mounted in said housing spaced from said open end and havingits periphery spaced from the housing interior to provide an annularopening; a hollow piston formed with a closed end face directedoutwardly of said housing open end and an elongated skirted portionsliding within said housing and fitting through said annular openingabout the periphery of said face plate; means in said face plate andhousing venting the hollow of said piston to atmosphere; and apre-crushed honeycomb element mounted in said hollow piston between saidend face and said face plate, said element consisting of a plurality ofWalls forming axially elongated cells oriented between said end face andface plate, said cell walls having permeations to permit air passagetherebetween and into said hollow piston, whereby said element willfreely crush further upon application of energy to said end face forcingthe latter toward said face plate.

7. A device for measuring energy, said device comprising a nondeformablefirst member having a socket and an abutment extending across one end ofthe socket, a nondeformable second member fitted into the socket of thefirst member to form an enclosed chamber therewith and having anabutmient located opposite to the abutment of the first member, thesecond member being adapted to shift relative to the first member forchanging the volume of the chamber concurrently with altering thedistance between the abutments, an opening between the chamber and theexterior to vent the chamber upon change in volume to substantiallyeliminate back pressure on the abutments with change in distancetherebetween, and a honeycomb section located within the chamber withits columns extending parallel to the direction of relative movement ofsaid members and its ends positioned at the abutments, the honeycombsection being precrushed by an amount to initially overcome its columnarstrength, whereby opposing forces acting upon the members and orientedsubstantially in the direction of relative movement of said members willbe transmitted to the honeycomb section through the abutments, causingthe honeycomb section to crush still further and provide an indicationof the amount of energy absorbed.

8. A device according to claim 7 wherein the sides of said honeycombsections are uncovered so that the outermost honeycomb columns areexposed to the chamber.

References Cited The following references, cited by the Examiner, are ofrecord in the patented file of this patent or the original patent.

5 UNITED STATES PATENTS 2,620,652 12/1952 Hartmann 73--35 2,870,6311/1959 Musser et al. 73167 3,082,846 3/1963 Jensen et a1 73l2X 3,130,8194/1964 Marshall 188-1 (C) 0 3,178,935 4/1965 McRitchie 7394 3,252,5485/1966 Pajak et a1 188-1 (C) FOREIGN PATENTS 10,442 1898 Great Britain.

JAMES J. GILL, Primary Examiner US. Cl. X.R. 188-1

